. PATHOGNESIS OF CEREBRAL ISCHEMIA: The discovery of ET-1 and NO has greatly contributed to our understanding of the functional changes of many organs under physiological and pathological conditions (e.g., hypertension, atherosclerosis, and stroke). Previous studies focused on interactions of endocannabinoids [2-arachidonoylglycerol (2-AG) and anandamide (ANA) with the vasoconstrictor, endothelin-1 (ET-1). Both 2-AG and ANA are produced in various organs (brain,gut) and cell [monocytes, platelets, endothelial cells (EC)]; they elicit neuromodulator, cytoprotective (i.e., brain ischemia and trauma) and cardiovascular including vasodilatory effects, which are mainly mediated through cannabinoid (CB) receptors CB1, CB2 receptors. 2-AG antioxidant properties have also been implicated to ameliorate BBB injury and edema formation induced by closed head injury (CHI). This supposition was confirmed by the observed 2-AG modulation of brain injury, BBB permeability and edema formation after CHI. In addition comparable effects between 2-AG and 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl(TPL), a known antioxidant nitroxide on human brain endothelial Ca2+ and cytoskeletal responses to H2O2 (ROS) where investigated in vitro. Both substances were shown to similarly modify endothelial responses mentioned above substantiating the implicated 2-AG antioxidant properties. Latest reports indicate that the vasodilatory effects of ANA in contrast to 2-AG is mediated through the vanilloid TRPV1 receptor. Untill now most of the endothelial-dependent and endothelial-dependent vascular responses have been shown to be mediated by CB1 receptors. In view of these observations, we hypothesize a possible endothelial existence of TRPV1 receptors along with CB1 and CB2 receptors and their involvement in human brain endothelial cells (HBEC) responses to endocannabinoids and related substances. These studies led to the first clear demonstration of the constitutive expression of TRPV1, CB1, and CB2, receptors (mRNA and protein)on HBEC. It also provided evidence that these receptors are functional and possibly cooperative in these cells. In addition the results demonstrated that 2-AG acts as a ligand for TRPV1 receptors as well as for cannabinoid receptors. The novel findings of colocalization and functional capacities of TRPV1, CB1, and CB2, receptors on HBEC strongly suggest that these receptors may affect the function of cerebral microvascular endothelium and contribute to the regulation of cerebral blood flow and BBB permeability. In vivo studies in progress are designated to confirm this contention. II. TOLERANCE TO CEREBRAL ISCHEMIA: The study of SHR-SP tolerization with E-selectin (in collaboration with Dr. J. Hallenbeck) demonstrated a reduced incidence and size of brain infarct and hemorrhage. The latest studies demonstrated that mucosal tolerization renders cell-mediated protection against cerebral damage (stroke). Continued investigation is focused on the mechamism involved in the observed above mentioned phenomena tolerized SHR-SP animals as compared to the Naive rats and whether the E-selectin-induced tolerization against brain injury in SHR-SP rats also effect peripheral organs (i.e., heart and kidneys). In addition, a new initiative for stroke prevention (induction of mucosal tolerance to E-selectin) involves a preclinical study with spontaneously hypertensive, genetically stroke-prone rats and an approved Phase II A Clinical Trial